1. Field of the Invention
The invention disclosed herein generally pertains to a method and apparatus for providing information related to the power capacity of a rechargeable battery, wherein the battery is disposed to supply power to an electronic device. More particularly, the invention pertains to a method of the above type that improves accuracy in providing such information. Even more particularly, the invention pertains to a method of the above type wherein such information is based on actual monitored performance of the battery.
2. Description of the Related Art
As is well known, rechargeable batteries are used as a power source for ever-increasing numbers and types of electronic products. These products can include, without limitation, laptops, notebooks, and other highly portable computers, mobile phones and personal data assistants (PDA). Rechargeable batteries are also used widely as emergency power sources, for electronic devices normally connected to power lines. In computer and other electronic products, the available power capacity of a rechargeable battery, at any given time, is typically expressed as a percentage of maximum power capacity, wherein maximum capacity represents available battery power right after completing a recharge operation.
The term “battery time” as used by those of skill in the art, and also as such term is used herein, means the amount of time that a battery can be used as a power source for a particular purpose, or in a particular mode, until the battery power is completely dissipated. At present, the percentage of power capacity, as discussed above, is typically used as a basis for estimating the available battery time. In laptop computers or the like, it is common to indicate the battery time that can be expended for a particular percentage of capacity for each of three different modes of computer use, e.g., normal, maximum and minimum modes.
Currently used approaches for estimating battery time are usually based on the capability of batteries to store and provide power when they are new. However, the ability of a battery to store power tends to decline significantly, as the battery is used repeatedly over time. For example, the battery time, or operational expectancy, of a new battery charged to 100% power capacity could be three hours. After the battery has been used on a daily basis for three or four years, however, and has been continually discharged to supply power and then charged back to full capacity, battery time for 100% capacity could in fact be only one hour. Toward the end of its life, maximum battery time may even be as low as 5-10 minutes.
Generally, prior art procedures for furnishing battery time do not consider how a battery has been operated over time. Thus, no historical record is kept of battery usage. As a result, it is very common for a user of a device with a rechargeable battery to discover that the battery has run out of power, well before the anticipated battery time has ended. It will be readily appreciated that such events can be inconvenient, very undesirable or even catastrophic.
As an example, it is well known by users of laptop computers that placing a laptop into standby mode reduces the power required to a fraction of the power needed for a normal mode of operation. At the same time, the laptop can be started up almost instantaneously from standby mode, without a need for booting. Accordingly, it has become common for a laptop user to place the laptop computer into standby mode, when the computer contains work in process for an uncompleted task, and the user must suspend work for a period of time. This occurs frequently, for example, when a user reaches the end of a work day at, e.g. 5 PM, and will resume work the next day at, e.g. 8 AM. For this situation, if the user places his computer into standby mode at 5 PM, the computer battery would need to supply power to operate in this mode for 15 hours. Assuming that the read out on the laptop computer shows sufficient power capacity, e.g. 50%, to provide a battery time of over 15 hours in standby mode, the user would anticipate no difficulties. However, because of advanced battery age, the power would in fact be completely dissipated before the end of the 15 hour period. This would cause the computer to completely shut down, so that the work in process would be lost. Thus, the result of inaccurate battery time information could be quite serious.